I'm green...appreciate your advice...

slockm on Sat July 17, 2010 12:43 PM

alight, this is going to be a weird story, so please bear with me:I purchased this vehicle last year. Come summertime, it was evident the system wasn't running. Evidence pointed to the fact that the compressor had blown a seal so I replaced the compressor with a new compressor purchased off of ebay (first mistake). I also purchased a condenser off of ebay to replace at the same time (second mistake). I did some moderate flushing of the system, but wasn't overly concerned b/c the orifice tube was not dirty. I replaced the o-tube, the drier, the compressor, and the condenser. I was unable to remove the rear expansion valve and did not replace any of the tubing (including the "muffler" tubing off the compressor).

The system ran pretty well that summer but the condenser had a very small leak. So when it came around to this summer, it wasn't cooling. I replaced the condenser, pulled vacuum, blah blah, recharged, about a month ago. When I, again, recharged the system, something just never seemed right. The compressor took forever to drink the cans of R134 and the high side pressure never really went up. I went ahead and put the full amount (right around five 12-oz cans) but the high side never did anything substantial. The air temp out of the vent is now about 20 degrees less than the outside air temp. So at 95 degrees F outside, the vent temp is 70-75 degrees F and the vent temp quickly rises if the truck is sitting at idle.

I have obtained a replacement compressor to drop in, as that seems like the problem. BUT, I don't want to replace that and then that not be the problem. What tests can I run on the system with the current compressor installed to determine exactly what the problem is? Thank you all so much for your help in advance!

Again, I have found that the vent temperature is generally 20-25 degrees cooler than ambient when I'm driving on the highway.

-------------------------I know nothing...seriously

Edited: Sun July 18, 2010 at 3:28 PM by slockm

bohica2xo on Sun July 18, 2010 4:00 PM

Looks like the compressor is not doing much. Do you have an orifice tube installed in the system?

B.

-------------------------"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest." ~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

slockm on Sun July 18, 2010 5:29 PM

Yes I do, and when I replaced the components last year I replaced the orifice tube as well.

-------------------------I know nothing...seriously

bohica2xo on Sun July 18, 2010 6:43 PM

Time to go look & see how much of that compressor is now located on the orifice tube screen.

You are not getting much pumping. I would say the HT6 has an issue.

B.

-------------------------"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest." ~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

slockm on Sun July 18, 2010 10:39 PM

You're suggesting black death? So I know the orifice tube was clean when first installed, if it is filthy now, then my compressor has burned up? NOOOOOO!!!!!!!!!!

-------------------------I know nothing...seriously

Dougflas on Sun July 18, 2010 11:50 PM

make sure you put the o tube in the correct direction. Compressor is not doing any work.

bohica2xo on Mon July 19, 2010 12:43 AM

Ok, let's start with last year:

Belly leaker > replaced with e-bag compressor

Condensor > replaced with e-bag part

Flushing? Incomplete. Rear system not flushed

Flush agent? Removed? unknown.

Remaining oil quantity? unknown. Total system oil quantity? unknown.

This year:

Leaking e-bag condensor replaced. Oil added at this time? unknown.

Charging issues. "took forever" to charge the system.

Low high side pressures, poor cooling - NO cooling at idle.

Does that sound accurate? That is what I see reading your post. Now, presuming you got all of the flushing agent out, and had enough oil in the system when the new compressor and condensor went on - how many times did you top up the leaking system?

I see a system that was leaking, probably topped up a time or two last season. You changed the condensor, and charged gas through the low side. Did you jumper the low pressure switch when you were putting the 5 cans of refrigerant in? Did you add any oil to the system?

B.

-------------------------"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest." ~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

slockm on Tue July 20, 2010 11:36 AM

Bohica -

Your analysis is fairly accurate. Basically could not afford to get the job done right, ended up doing a less-than-adequate job.

No flushing took place initially based on the fact that the system "looked clean" at the orifice tube and the condenser was replaced.

I don't recall how much oil I added, but I added oil per instructions to each replaced component. In the latest swap of the condenser, I added a small amount of oil to the condenser as well.

I have never "topped off" the refrigerant. I've only added a known quantity each time. I did not jumper the low pressure switch when filling - I just let the can pressurize the system until the compressor kicked in (I just assumed the can put just enough in to actually cause the compressor to kick on).

I've had a few people suggest perhaps my fan clutch is not functioning properly. How can I test this? I doubt if that tells the whole story because even at highway speeds my cooling is pretty cruddy (Tulsa forecasts heat indexes of 105+ all week).

Thanks.

-------------------------I know nothing...seriously

bohica2xo on Tue July 20, 2010 1:02 PM

If you did not top up, and added oil for removed components, then you probably have plenty of oil in the system - perhaps even too much.

Fan clutches get weak, and do cause issues. Usually the vehicle cools just fine at highway speeds with a dead fan clutch however.

Too much oil, bad fan clutch - both of these would make the high side skyrocket. Your high side is LOW. That excludes the fan & oil, however both may be an issue once the lack of pumping is solved.

You said it took 5 cans, and your static pressure indicates it has some refrigerant in it. Even a low charge on a good compressor will show a larger differential than your testing.

That leaves a damaged compresssor as the most likely item. Not "black death" - that is only for Ford FX15 compressors. But perhaps a broken reed valve petal. Like I said, time to pull the orifice tube, and have a look for metal shards. Perhaps you will get lucky, and find that the orifice tube has failed, and is just a huge hole now. Not common, but it could be the source of your problem... PULL the O/T.

You already know the best repair is a total teardown, flush & some new parts. I understand it is hot, but there is no quick solution. You can pull the compressor, and check it on the bench. Put your finger over the discharge port, and turn it by hand. It should hold pressure when you stop turning. Same thing for the suction side of things.

When you charge a system like this, charge with the engine stopped into an evacuated system - as liquid into the HIGH side. Get as much liquid in as you can this way - before you start the engine. This gives the compressor a fighting chance of seeing some oil return. Once you can't get any more liquid into the system, close the high side valve.

Then start the engine & finish charging into the LOW side. do NOT jumper the cycle switch, just let it cycle. Doors open, cabin fan on high, idling.

B.

-------------------------"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest." ~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

slockm on Tue July 20, 2010 2:14 PM

Okay, that all sounds like great info and the best place to start!

A couple of notes:- I definitely have never charged with the engine off as liquid into the high side. Just hold the cans upside down or what?- When I shut the truck off, I can hear the expansion through the orifice tube (a hissing). I assume this means the OT is most likely creating the restriction I need.- If the OT looks good and the compressor looks good, what then? Should I flush the entire system (ugh) and start new?- How long can I generally have the system open (while performing diagnostics) before I need to replace the drier? I assume there is a certain point past which the vacuum pump is not going to adequately get the moisture out of the system...

Thanks again - wish I had found this forum a lot sooner...

Michael

-------------------------I know nothing...seriously

slockm on Wed July 21, 2010 10:58 PM

I do believe these pictures will provide an update to my findings:

So what is it exactly in a compressor that causes these metal shavings?

Next steps:Flush the entire system. What type of flushing method is recommended for DIY? Aerosol?Should the mufflers be flushed? Replaced? Do they HAVE to be replaced?Should the rear TXV be replaced? I was unable to break the fitting loose last year and I'm thinking it probably has not loosened up any. Recommendations?Should I remove the condenser to flush or flush in place?Should the accumulator be replaced? How about the evaporator? How is the evaporator accessed in a 1998 GMC Yukon?

Thanks again (ugh),Michael

-------------------------I know nothing...seriously

HECAT on Wed July 21, 2010 11:19 PM

QuoteOriginally posted by: slockmSo what is it exactly in a compressor that causes these metal shavings?

bohica2xo on Thu July 22, 2010 1:47 AM

The orifice tube is the primary filter for the front evaporator in this system.

Unfortunately, the condensor becomes the primary system filter. As condensors have become multi-pass units they are also a labyrinth that becomes a filter. Old tube & fin units did not trap much. A 6mm piccolo becomes very hard to flush without specialized equipment.

The rear TXV also may have a screen. The connection will need to be broken to flush the lines, evaporator & valve. Flushing through the installed valve just does not work, the restriction prevents building enough velocity to remove the contaminates.

Mufflers can't be flushed. They can be eliminated with a straight piece of line.

The shavings? Well, the cylinders & pistons are aluminum. The shaft, swash plate & bearings are steel. Generally, if the OT has a mixture of steel shards & aluminum, but the pump still runs quietly it was a reed valve that failed. The reed petal gets into a cylinder, and destroys the piston, bore & itself. The swarf goes downstream with the refrigerant...

B.

-------------------------"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest." ~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.